The magnetic quantum number of an electron (m) designates the:

electron's main energy level

electron's direction of spin

orientation in space of the orbital (electron cloud)

overall shape of the orbital (electron cloud)

I think the correct answer from the choices listed above is the third option. The magnetic quantum number of an electron (m) designates the orientation in space of the orbital (electron cloud). This number divides the subshell into individual orbitals which hold the electrons; there are 2l+1 orbitals in each subshell. 

Iwould say the answer is d